Bipolar people generally have periods, which unfortunately can last their lifetimes, where they have a “chainsaw personality”. Sort of a “Texas Chainsaw Massacre” perpetrator personality where maximum hurt is intended and delivered. This is related to the “dysphoric mania” idea, when the sufferer is manic, alert and active and filled with rage and depressed at the same time. Theis very unhappy person generally is only interested in sharing the pain, with interest.
The use of recreational drugs and alcohol in any amount whatever hasten the progression of the disorder; unfortunately, alcohol will, in their younger days, cause a shift from dark depression to “euphoric”,”happy” mania or hypomania, so bipolars tend to “self-medicate” with alcohol, marijuana, etc., resulting in their disorder getting worse more quickly. The more alcohol and drugs are used the faster the downhill slide. You end up with a person with advanced bipolar disorder who is also an alcoholic.
I rather think Kim Il Sung and Jong Il were/are bipolar themselves. The elder Kim’s daughter is, and the younger Kim’s sister. The disorder runs in families.
Some experts think a large portion of the world’s population are bipolar - I have seen one in seven mentioned. If they stay away from drugs and alcohol they can do OK. Goering, Hitler, and Stalin did not.
Not all bipolars turn into monsters. Winston Churchill comes to mind, and he drank heavily.
Bipolars who abstain from alcohol and drugs can function fairly well for many years but tend to have a very dark view of human nature. This showed up as an intense realism in Churchill’s case. Less honorable men end up like the Glorious Leader and his son.
The disorder tends to progress with age until not uncommonly all they want to do is hurt people unless they are simply too depressed to care at all (not uncommon). The disorder is readily treated nowadays with mood stabilizers and other psychotropic drugs combined with absolutely no alcohol or recreational drugs.
I think that sounds about right, looking back my encounter with those bipolar folks.